SIM 5.1 can not login after root password change

Hello,I have changed the root password on the operating system. So I can not Login in to the sim. After 1 minute I logged in an exception report will displayed in the browser: The server encountered an internal error. I have changed the password to the old password, but the error is the same ;-(I have allready changed the Passwort from the sim: mxpassword -m -x MxPMPPassword="******"But the Problem is the same....